17. от 2 дм до 11см 9 дм.
18. незнаю
<span>240*710+7100*76 = 71 (2400+7600) = 71 * 10 000 = 710 000.
</span><span>
38*5800+380*520 = 38 (5800 + 5200) = 38* 11 000 = 38 * (10 000 + 1000) = 380 000 + 38 000 = 418 000.
</span>
1. 650 + (530 - 210) = 970
2. (560 + 120) - 240 = 440
3. (650 - 210) + (240 + 20) = 900
4. 1000 - (650 - 120) = 470
5. (168 + 120) + 240 = 528